<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // var str = 'qwert'
    // console.log( str.length )  // 字符串长度

    // 字符串跟任何类型拼接都是字符串
    console.log('qwe' + 'r')  // qwer
    console.log('qwe' + 8) // qwe8
    console.log(  8 + 8)  // 16
    console.log(  '' + 8)  // '8'
    console.log( '' + 8 + 8)  // '8' + 8  88
    console.log( 8 + 8 + '')  // '16'
  </script>
</body>
</html>